🏗️ Foundation Calculator

Calculate foundation loads, footing sizes, bearing capacity, and reinforcement requirements for safe structural design.

Calculator
Soil Types
Load Types
Reinforcement
Codes & Standards

Foundation Calculator

Select calculation type and enter structural parameters to calculate foundation requirements with engineering accuracy.
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Bearing Capacity
Calculate soil bearing capacity
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Footing Size
Calculate required footing dimensions
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Reinforcement
Calculate rebar requirements
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Settlement
Estimate foundation settlement
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Stability
Check overturning and sliding

Foundation Cross-Section

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Foundation loads and dimensions visualization
Cross-section showing foundation elements and load distribution

Soil Types & Bearing Capacity

Common soil types with typical bearing capacities and engineering properties for foundation design.

Granular Soils

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Dense Sand
4000-6000 psf
Well-compacted sand with good drainage. Excellent bearing capacity. N-value > 30. Suitable for most foundation types.
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Medium Dense Sand
2000-4000 psf
Moderately compacted sand. Good bearing capacity with proper design. N-value 10-30. Requires settlement analysis.
🌊
Loose Sand
1000-2000 psf
Poorly compacted sand. Limited bearing capacity. N-value < 10. May require ground improvement.
🪨
Gravel
6000-10000 psf
Excellent bearing material. High capacity and good drainage. Ideal for heavy structures. Minimal settlement.

Cohesive Soils

🧱
Hard Clay
4000-8000 psf
Stiff, overconsolidated clay. Good bearing capacity but poor drainage. Unconfined strength > 4000 psf.
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Medium Clay
1500-4000 psf
Firm clay with moderate bearing capacity. Settlement and drainage considerations important. Strength 1000-4000 psf.
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Soft Clay
500-1500 psf
Weak clay requiring special foundation design. High settlement potential. Strength < 1000 psf. Consider piles.
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Bedrock
15000+ psf
Excellent foundation material. Very high bearing capacity. Minimal settlement. May require blasting for excavation.

Foundation Load Types

Understanding different load types and their combinations for comprehensive foundation design.
🏠 Dead Load (DL)
DL = Structure Weight + Fixed Equipment
Permanent loads including building weight, fixed equipment, and built-in components. Typically 10-25 psf for residential, 50-150 psf for commercial.
👥 Live Load (LL)
LL = Occupancy + Furniture + Equipment
Variable loads from occupancy and movable equipment. Residential: 40 psf floors, Commercial: 50-100 psf depending on use.
🌬️ Wind Load (WL)
WL = q × G × Cp × Af
Lateral loads from wind pressure. Creates overturning moments. Varies by building height, exposure, and wind speed (85-200 mph design).
🌍 Seismic Load (EQ)
EQ = Cs × W
Earthquake forces based on seismic design category and building weight. Creates both vertical and horizontal forces on foundation.
❄️ Snow Load (SL)
SL = pf × Ce × Ct × Is
Snow loads on roof transmitted to foundation. Varies by location: 20-100 psf ground snow load depending on climate zone.
⚖️ Load Combinations
Max: 1.2DL + 1.6LL + 0.5SL
Critical load combinations per ASCE 7: Basic, Wind, Seismic combinations. Foundation must handle worst-case scenario.

Reinforcement Design

Rebar requirements and specifications for different foundation types and loading conditions.

🔧 Rebar Size & Spacing

Bar Size Diameter Area (sq in) Weight (lb/ft) Typical Use
#3 0.375" 0.11 0.376 Light footings, temperature steel
#4 0.500" 0.20 0.668 Residential footings, slabs
#5 0.625" 0.31 1.043 Medium footings, walls
#6 0.750" 0.44 1.502 Heavy footings, columns
#7 0.875" 0.60 2.044 Large footings, grade beams
#8 1.000" 0.79 2.670 Heavy structural elements

📏 Minimum Requirements

🏠 Spread Footings
As,min = 0.0018 × Ag
Minimum 0.18% reinforcement ratio. #4 bars @ 12" o.c. each way minimum. Cover: 3" bottom, 2" top and sides.
📐 Strip Footings
As = 0.002 × b × h
Continuous footings under walls. #5 bars @ 12" o.c. longitudinal, #4 @ 18" transverse. 6" min thickness.
🏢 Mat Foundations
As = M / (fy × jd)
Two-way reinforcement required. Top and bottom mats. #6 @ 6-12" o.c. typical. Temperature steel minimum 0.0018Ag.
🔩 Development Length
ld = (fy × db) / (25√f'c)
Minimum embedment for full bar strength. Hooks may reduce length. Critical at discontinuities and joints.

Codes & Standards

Building codes, design standards, and safety requirements for foundation engineering.

📋 Design Codes

🏛️ International Building Code (IBC)
Primary building code in US. Sets minimum requirements for foundation design, soil investigation, and structural loads. Updated every 3 years.
🔧 ACI 318 - Concrete Code
Design requirements for reinforced concrete foundations. Covers reinforcement ratios, development lengths, and strength design methods.
🌬️ ASCE 7 - Minimum Design Loads
Load combinations, wind loads, seismic loads, and other environmental loads. Essential for foundation load calculations.
🌍 ASCE 41 - Seismic Evaluation
Seismic evaluation and retrofit of existing buildings. Performance-based design approaches for foundation upgrades.
🔬 ASTM Standards
Material testing standards for concrete, steel, and soil. ASTM D1586 (SPT), ASTM C39 (concrete strength), ASTM A615 (rebar).
⚠️ Safety Requirements
Professional engineer approval required for most foundations. Soil investigation mandatory for commercial projects. Special inspection required.